September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Clinical, genetic and functional study of ABCA4 mutations in Stargardt patients
Author Affiliations & Notes
  • Kailun Jiang
    University of British Columbia, Coquitlam, British Columbia, Canada
  • Laurie L Molday
    University of British Columbia, Coquitlam, British Columbia, Canada
  • Heidi Barbara Stoehr
    University of Regensburg, Regensburg, Germany
  • Bernhard HF Weber
    University of Regensburg, Regensburg, Germany
  • David Maberley
    University of British Columbia, Coquitlam, British Columbia, Canada
  • Robert S Molday
    University of British Columbia, Coquitlam, British Columbia, Canada
  • Footnotes
    Commercial Relationships   Kailun Jiang, None; Laurie Molday, None; Heidi Stoehr, None; Bernhard Weber, None; David Maberley, Alcon (C), Allergan (C), Bayer (C); Robert Molday, None
  • Footnotes
    Support  NEI grant EY02422
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 3174. doi:
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      Kailun Jiang, Laurie L Molday, Heidi Barbara Stoehr, Bernhard HF Weber, David Maberley, Robert S Molday; Clinical, genetic and functional study of ABCA4 mutations in Stargardt patients. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3174.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : ABCA4 is member of the superfamily of ATP-binding cassette (ABC) transporters that functions in the clearance of retinal derivatives from photoreceptor disc membranes. Over 800 mutations in ABCA4 are known to cause Stargardt macular degeneration and related retinal degenerative diseases. The purpose of this study is to identify disease-causing mutations in Stargardt patients in British Columbia and correlate the disease phenotypes of these individuals with photoreceptor mislocalization and loss in function of ABCA4.

Methods : Stargardt patients were evaluated for visual acuity, microperimetry, visual fields, full-field electroretinography, fundus photography, autofluorescence imaging, and spectral domain optical coherence tomography. DNA from the blood of Stargardt patients was screened for mutations in ABCA4. The cDNAs for selected missense mutations were generated using site-directed mutagenesis and transiently expressed in HEK293T cells. Wild-type and mutant ABCA4 proteins were purified and incorporated into liposomes for analysis of their functional activity. For cell localization studies, plasmids in which ABCA4 was fused to the green fluorescent protein (GFP) were electroporated into the retina of P1 Abca4 knockout mice. At P21, the mice were sacrificed and examined for ABCA4 localization and retinal morphology by confocal microscopy.

Results : The 14 individuals enrolled in this study displayed phenotypes characteristic of Stargardt patients. One compound heterozygous patient was found to have missense mutations at A1038V and L541P. Wild-type ABCA4-GFP primarily localized to the outer segments of photoreceptors, whereas the A1038V mutant was found in both the inner and outer segments. The A1038V variant exhibited approximately 50% of the basal ATPase activity of the wild-type ABCA4 and was only slightly activated by retinal.

Conclusions : The A1038V ABCA4 mutation identified in one of the Stargardt patients cause protein mislocalization and significantly reduced functional activity. The second L541P mutant is currently under investigation. Correlation of disease phenotypes with cellular localization and functional properties provides a basis for further understanding the molecular and cellular mechanisms underlying Stargardt disease and the development of therapeutic treatments for this disease.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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